It was a famous enough piece of graffiti in the first place. One website used some questionable maths to estimate that something written in that exact place for ten years would have been seen by around 2,956,500,000 people (300,000 cars per year with 2.7 people - assuming that no one person drives past twice).

There is still an outstanding reward, by the way, for anyone who creeps back there during the night and repaints M. Khan Is Bent on the bridge.

While researching this writeup, I came across a website that contained this rather morbid explanation:

While studying criminal law, I think I found the answer to M khan being bent:-

DPP v Camplin 1978 A.C. 705 (House of Lords)
Lord Diplock:
"Camplin, who was 15 years of age, killed a middle-aged Pakistani, Mohammed Lal Khan, by splitting his skull with a chapati pan...At the time the two of them were alone together in Khan's flat...According to the story that he had told...Khan had buggered him in spite of his resistance and had then laughed at him. Whereupon Camplin had lost his self-control and attacked Khan fatally with the chapati pan..."